General Methods

Instance-level utilities for deleting data and inspecting storage, plus the module-level helpers exported from react-native-mmkv-storage.

import { MMKVLoader } from 'react-native-mmkv-storage';

const storage = new MMKVLoader().initialize();

Instance methods

removeItem

Removes a single key. Synchronous.

removeItem(key: string): boolean | undefined

Name	Type	Required	Description
key	string	yes	Key to delete.

Returns: boolean | undefined — true on success, undefined if the instance is not loaded.

storage.setString('user', 'robert');
storage.removeItem('user'); // => true
storage.getString('user'); // => null

removeItems

Removes many keys in one native call. Prefer this over looping removeItem for bulk deletes. Synchronous.

removeItems(keys: string[]): boolean | undefined

Name	Type	Required	Description
keys	string[]	yes	Keys to delete.

Returns: boolean | undefined

storage.setString('user1', 'robert');
storage.setString('user2', 'alex');

storage.removeItems(['user1', 'user2']); // => true

clearStore

Removes every key and value from the instance.

clearStore(): boolean | undefined

Parameters: none.

Returns: boolean | undefined

storage.clearStore(); // => true

clearMemoryCache

Drops the in-memory cache of the instance. Data on disk is untouched; it is re-read on the next access.

clearMemoryCache(): boolean | undefined

Parameters: none.

Returns: boolean | undefined

storage.clearMemoryCache(); // => true

getCurrentMMKVInstanceIDs

Returns the instances that have been loaded in the current app session, as an object keyed by instance ID whose values report whether that instance has finished initializing.

getCurrentMMKVInstanceIDs(): { [id: string]: boolean }

Parameters: none.

Returns: { [id: string]: boolean }

storage.getCurrentMMKVInstanceIDs(); // => { default: true }

Object.keys(storage.getCurrentMMKVInstanceIDs()); // => ['default']

getAllMMKVInstanceIDs

Returns the IDs of every instance ever created on this device, whether or not it was loaded this session.

getAllMMKVInstanceIDs(): string[]

Parameters: none.

Returns: string[]

storage.getAllMMKVInstanceIDs(); // => ['default', 'user-storage']

getKey

Returns the encryption key of the instance and the alias it is stored under in the Keychain/Keystore. Both are null for an unencrypted instance.

getKey(): { alias: string | null; key: string | null }

Parameters: none.

Returns: { alias: string | null; key: string | null }

import { MMKVLoader } from 'react-native-mmkv-storage';

const secure = new MMKVLoader().withInstanceID('secure').withEncryption().initialize();

secure.getKey(); // => { alias: '636f6d2e...', key: 'gY7...' }

AsyncStorage-compatible methods

These exist so the instance can be dropped into libraries that expect an AsyncStorage-shaped object, such as redux-persist and zustand's persist middleware.

setItem

Stores a string value. Non-string values will throw — use setMap or setArray for structured data.

setItem(key: string, value: string, callback?: (err?: Error | null) => void): Promise<boolean | undefined>

Name	Type	Required	Description
key	string	yes	Key to write to.
value	string	yes	The string to store.
callback	(err) => void	no	Called with null after the write.

Returns: Promise<boolean | undefined>

await storage.setItem('user', 'robert'); // => true

getItem

Reads a string value.

getItem(
  key: string,
  callback?: (error?: Error | null, result?: string | null) => void
): Promise<string | null | undefined>

Name	Type	Required	Description
key	string	yes	Key to read.
callback	(error, result) => void	no	Called with the value.

Returns: Promise<string | null | undefined>

const user = await storage.getItem('user'); // => 'robert'

WARNING

setItem and getItem return promises, but removeItem is synchronous and returns a boolean, not a promise. Most consumers tolerate this because await on a non-promise resolves immediately, but if you write a custom storage adapter, wrap it yourself: removeItem: async key => storage.removeItem(key).

Module methods

Imported directly from the package rather than from an instance.

init

Installs the JSI bindings. This happens automatically the first time you call initialize() on a loader, so you rarely need it — reach for it only if you want to install the bindings eagerly at app start.

init(): boolean

Parameters: none.

Returns: boolean — true if the bindings are installed, false if installation failed (the error is logged to the console).

import { init } from 'react-native-mmkv-storage';

init(); // => true

isLoaded

Reports whether the JSI bindings are currently installed, without attempting to install them.

isLoaded(): boolean

Parameters: none.

Returns: boolean

import { init, isLoaded } from 'react-native-mmkv-storage';

if (!isLoaded()) {
  init();
}

getCurrentMMKVInstanceIDs

The module-level form of the instance method, usable before any instance exists.

getCurrentMMKVInstanceIDs(): { [id: string]: boolean }

Parameters: none.

Returns: { [id: string]: boolean }

import { getCurrentMMKVInstanceIDs } from 'react-native-mmkv-storage';

getCurrentMMKVInstanceIDs(); // => { default: true }

getAllMMKVInstanceIDs

The module-level form of the instance method.

getAllMMKVInstanceIDs(): string[]

Parameters: none.

Returns: string[]

import { getAllMMKVInstanceIDs } from 'react-native-mmkv-storage';

getAllMMKVInstanceIDs(); // => ['default', 'user-storage']

IDSTORE_ID

The ID of the internal storage the library uses to record which instances exist and whether they are encrypted. Exported so you can exclude it when iterating instances.

const IDSTORE_ID: string

Type: string — the value differs per platform (mmkvIdStore on iOS, mmkvIDStore on Android), so compare against this export rather than hard-coding a literal.

import { getAllMMKVInstanceIDs, IDSTORE_ID } from 'react-native-mmkv-storage';

const ids = getAllMMKVInstanceIDs().filter(id => id !== IDSTORE_ID);

WARNING

Never write to the ID store yourself. Corrupting it can make encrypted instances unloadable.

Deprecated

The default export and its members still work but are deprecated. Use the named exports instead.

Deprecated	Replacement
MMKVStorage.Loader	import { MMKVLoader } from 'react-native-mmkv-storage'
MMKVStorage.API	import { MMKVInstance } from 'react-native-mmkv-storage'
MMKVStorage.MODES	import { ProcessingModes } from 'react-native-mmkv-storage'
MMKVStorage.ACCESSIBLE	import { IOSAccessibleStates } from 'react-native-mmkv-storage'
MMKVStorage.getAllMMKVInstanceIDs	import { getAllMMKVInstanceIDs } from 'react-native-mmkv-storage'
MMKVStorage.getCurrentMMKVInstanceIDs	import { getCurrentMMKVInstanceIDs } from 'react-native-mmkv-storage'
MMKVStorage.IDSTORE_ID	import { IDSTORE_ID } from 'react-native-mmkv-storage'

import MMKVStorage from 'react-native-mmkv-storage';

const storage = new MMKVStorage.Loader()
  .setProcessingMode(MMKVStorage.MODES.MULTI_PROCESS)
  .initialize();

The equivalent, using named exports:

import { MMKVLoader, ProcessingModes } from 'react-native-mmkv-storage';

const storage = new MMKVLoader()
  .setProcessingMode(ProcessingModes.MULTI_PROCESS)
  .initialize();